The following abbreviations and terms are herewith defined, at least some of which are referred to within the following description of the present disclosure.
3GPP 3rd-Generation Partnership Project
BLER Block Error Ratio
ASIC Application Specific Integrated Circuit
BTTI Basic TTI
CDMA Code Division Multiple Access
DFT Discrete Fourier Transform
DL Downlink
DSP Digital Signal Processor
EDGE Enhanced Data rates for GSM Evolution
EGPRS Enhanced General Packet Radio Service
FDMA Frequency Division Multiple Access
FN Frame Number
GSM Global System for Mobile Communications
IMSI International Mobile Subscriber Identity
MISO Multiple Input Single Output
MTC Machine Type Communications
LTE Long-Term Evolution
OFDMA Orthogonal Frequency Division Multiple Access
PDN Packet Data Network
RACH Random Access Channel
SCPIR Sub-Channel Power Imbalance Ratio
SIMO Single Input Multiple Output
SNR Signal-to-Noise Ratio
TDMA Time Division Multiple Access
TS Time Slot
TTI Transmission Time Intervals
UE User Equipment
UL Uplink
WCDMA Wideband Code Division Multiple Access
WiMAX Worldwide Interoperability for Microwave Access
Receiver: A wireless apparatus such as a wireless access node (e.g., base station) has a receiver to receive signals over a physical channel from one or more other wireless apparatuses such as wireless devices (e.g., users, mobile stations). Likewise, the wireless devices (e.g., users, mobile stations) each have a receiver to receive a multiplexed signal over the physical channel from the wireless access node (e.g., base station).Transmitter: A wireless apparatus such as a wireless access node (e.g., base station) has a transmitter to transmit a multiplexed signal over a physical channel to one or more other wireless apparatuses such as wireless devices (e.g., users, mobile stations). Likewise, the wireless devices (e.g., users, mobile stations) each have a transmitter to transmit a signal over the physical channel to the wireless access node (e.g., base station).
Existing radio access technologies deploy different multiplexing (multiple) access schemes to divide the radio spectrum among multiple users (e.g., mobile stations). For example, Global System for Mobile Communications (GSM) utilizes Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) to divide the radio spectrum among multiple users (e.g., mobile stations). Long-Term Evolution (LTE) utilizes TDMA and Orthogonal Frequency Division Multiple Access (OFDMA) to divide the radio spectrum among multiple users (e.g., mobile stations).
When the multiplexing (multiple) access scheme has a TDMA component, the transmitted signal is divided into blocks, which may be transmitted sequentially in time on the same channel to different receivers. The multiplexing is provided by alternating between blocks to different receivers.
On most radio channels, the transmitted signal is distorted by the channel propagation before the transmitted signal reaches the receiver. The channel may, for example, add time dispersion and/or attenuation to the transmitted signal. Typically, the impact of this distortion varies with time, e.g., due to movement of the transmitter and/or the receiver. In addition, the transmitter and receiver may themselves introduce random changes in the phase of the signal from one block to the next.
In some situations, e.g., when the transmitter and receiver are stationary, the channel variations are very slow or even non-existent. In such scenarios, a conventional technique to increase the coverage is to use block repetition on the transmitter side and coherent accumulation of multiple received signal samples on the receiver side. For coherent combining, the phase of the transmitted blocks generally needs to remain the same or change in a known way.
With block repetition, the signal-to-noise ratio (SNR) after coherent combining will increase as 10*log 10(N), where N is the number of repetitions.
Block repetition has been proposed, for example, in LTE in order to achieve coverage increases of up to 15-20 dB for Machine Type Communications (MTC), as described in the 3rd-Generation Partnership Project (3GPP) TR 36.888 V12.0.0 Technical Report “Study on provision of low-cost Machine-Type Communications (MTC) User Equipments (UEs) based on LTE.” The contents of the 3GPP TR 36.888 V12.0.0 Technical Report are hereby incorporated by reference for all purposes. The same principle would equally apply to, for example, GSM to achieve coverage improvements.
However, while block repetition increases the effective SNR, block repetition also reduces the capacity of the channel. The capacity of the channel is inversely proportional to the number of repetitions N. Therefore, there is a need in multi-user multiplexing techniques to increase the coverage while maintaining capacity of the channel. This need and other needs are addressed by the present disclosure.